Mechanical interlock for electrical switches or the like



May 5, 1970 D. D. WARD MECHANICAL INTERLOCK FOR ELECTRICAL SWITCHES OR LIKE Filed Dec. 14. 1967 United States Patent 3,510,612 MECHANICAL INTERLOCK FOR ELECTRICAL SWITCHES OR THE LIKE Daniel Douglas Ward, Milwaukee, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Dec. 14, 1967, Ser. No. 690,667 Int. Cl. H01h 9/26 U.S. Cl. 200-50 Claims ABSTRACT OF THE DISCLOSURE An interlock mechanism for electrical switches or the like including two interlockable cam members which are supported on fixed pivotal axes by means of a bracket member which in turn is supported at its opposite ends by the respective companion switches which are being interlocked. Each of the companion switches is provided with an operator member which is moved into engagement with one of the respective pivoted cams upon the energization of its respective switch. Actuation of either of the interlocking cams by energization of its associated switch will cause that respective cam to move into the path of movement of the other cam in such manner as to prevent movement of the companion switch into circuit closing position.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to interlock mechanisms and more particularly to interlocked electrical switches.

The interlock mechanism of the invention will be described as embodied in an interlock mechanism for electrical switches although the interlock mechanism is suitable for use in other environments.

Description of the prior art In the art of electrical switching, it frequently happens that two electrical switches are electrically related to each other or to a utilization circuit or apparatus in such manner that both of the electrical switches should never be closed at the same time. An example of two such electrical switches are the starting switches used for energizing a reversing motor, since one switch connects the motor to electrical power for rotation in one direction and the other switch connects the motor to electrical power for rotation in the other direction, and if both switches were closed at the same time a short circuit would occur through the two closed switches. Hence, it is necessary to insure that two such switches are not both closed at the same time, but that one of the switches is always open when the other switch is closed.

A problem which has been encountered in the construction of mechanical interlock devices for two associated switches in accordance with the teachings of the prior art is that the proper functioning of the interlocking elements frequently depends on the exact physical positioning of one of the switches and its interlock operator with respect to the other switch and its cooperating interlocking element. Thus, if the two switches are not exactly located in the predetermined required physical relation with respect to each other, the interlock mechanism of such prior art switches frequently will not function or will function improperly.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an improved interlock mechanism for interlocking two companion devices such as electrical switches, in which the proper operation of the interlock device does not depend upon a critical spacing between the devices being interlocked.

It is another object of this invention to provide an interlock mechanism for electrical switches or the like in which the interlocking elements associated with the respective switches are maintained in a fixed relation with respect to each other despite variations in the physical spacing of the companion switches with respect to each other.

In achievement of these objectives, there is provided in accordance with an embodiment of this invention an interlock mechanism for electrical switches or the like in which two interlockable cam members are supported on fixed pivotal axes by means of a bracket member which in turn is supported at its opposite ends by the respective companion switches which are being interlocked. Each of the companion switches is provided with an operator member which is moved into engagement with one of the respective pivoted cams upon the energization of its respective switch. Actuation of either of the interlocking cams by energization of its associated switch will cause that respective cam to move into the path of movement of the other cam in such manner as to prevent movement of the companion switch into circuit closing position.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a pair of companion switches provided with a. mechanical interlock mechanism in accordance with the invention;

FIG. 2 is a side elevation view of the two switches of FIG. 1 and their interlock mechanism;

FIG. 3 is a view taken along line IIIIII of FIG. 2 showing the interlock mechanism in neutral or unoperated position;

FIG. 4 is a bottom plan view of the interlock mechanism and the supporting bracket therefor; and

FIG. 5 is a view generally similar to FIG. 3 except that the interlock mechanism is shown in operated position due to actuation of one of the companion switches so as to prevent operation of the other of the switches.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is shown a first switch generally indicated at 10 and a second switch generally indicated at 10. The switch 10 in the embodiment shown includes three input terminals 12, 14 and 16 and the switch 10 includes three input terminals 12', 14' and 16'. Switch 10 is connected to the electrical power source 18 through conductors Ll, L2 and L-3 which are respectively connected to terminals 12, 14 and 16 of the switch. Switch 10' is connected to power line Ll by conductor 24 which is connected to terminal 16 of switch 10'; to input power line L2 by conductor 20 which is connected to terminal 12' of switch 10' and to power line L3 by conductor 22 which is connected to terminal 14 of switch 10'.

Switch 10 is provided with output terminals 26, 28 and 30 which are respectively connected to the output lines L4, L5 and L6. Switch 10' is provided with output terminals 32, 34 and 36 which are respectively connected by conductors 38, 40 and 42 to output power lines L6, L5 and L4.

It will be noted that if switch 10 is closed the output power lines L4, LS and L6 are respectively connected to the input power lines L-l, L-2 and L3, whereas if switch 10' is closed, output power lines L4, L-5 and L6 are respectively connected to power lines 1P1, L-3 and L-2. Thus, if switches 10 and 10' are respectively employed in the forward and reverse energization circuits of a reversing type motor, and assuming that power lines L-l, L-2 and L-3 are connected to three phase electrical power, the closure of switch 10" will be effective to provide a phase reversal of the output lines L-4, L-5 and L-6.

The switches and 10 are each respectively provided with housings 44 and 44 closed at the upper end thereof by cover members 46 and 46, respectively. The cover members 46 and 46' carry on the under surfaces thereof stationary contact elements which are connected to the respective input and output terminals of the corresponding switch when the cover member is fastened in position on the respective switch housing 44 and 44. That is, for example, the cover member 46 carries a set of three stationary contacts which engage the terminals 12, 14 and 16 and another set of three stationary contacts which engage the output terminals 26, 28 and 30. Switch 10' and its cover member 46 are provided with banks of contacts similar to those just described for switch 10 and its cover member 46. Each of the switches 10 and 10" is also provided internally of switch housing 44 or 44' with a solenoid operated bank of movable bridging contacts which when closed complete the electrical connection from the input terminals of the switch to the output terminals thereof through the aforementioned stationary contacts on the under surface of the cover member.

In accordance with the invention, an interlock mechanism generally indicated at 50 is connected between the two switch housings 44 and 44' to insure that whenever one of the two switches 10' and 10' is in closed position the other of the two switches is open. This interlock mechanism 50 will now be described.

A support bracket 52 which may be formed of metal or other suitable material, extends between the two switches 10 and 10' and includes a planar portion 53 provided at each of its four corners with integral tablike projections 54 positioned at a level above that of planar portion 53 and which rest upon recessed or countersunk upper surface areas 56 in the contiguous flangelike end edges of the respective cover plates 46 and 46'. A second tablike projection 55 also integral with bracket 52, but extending in a plane substantially coplanar with planar portion 53, is positioned contiguous each of the tablike projections 54. Each projection 55 underlies the undersurface of the flangelike edge portion of the respective cover plate 46 or 46'; while the corresponding and contiguous projection 54, as previously mentioned, lies in a recessed or countersunk upper surface area of the contiguous flangelike end edge of one of the respective cover plates 46 or 46. Thus, each of the facing end edges of the cover plates 46 and 46 of the two interlocked switches 10 and 10' is gripped by two pairs of cooperating tablike projections 54 and 55 which secure the support bracket 52 and the interlock elements carried thereby firmly in position relative to switches 10 and 10'.

Bracket 52 has secured thereto a downwardly extending normally vertical bracket portion 58 comprising a bight portion 60 which is fastened by screws 62 to the planar portion 53 of bracket 52. In describing the bight portion, the length of the bight shall be considered the dimension extending from the top to the bottom of the drawing in the view of FIG. 1. The width of the bight shall be considered the dimension extending from left to right in the view of FIG. 1. The vertical bracket 58 includes downwardly extending bracket wall portions 64 and 66, respectively, each of which extends for substantially onehalf or slightly less than one-half the length of the bight portion 60. The downwardly extending bracket wall portions 64 and 66 extend inwardly from opposite ends of the length of the bight portion and on opposite sides of the width of the bight portion so as not to be in overlapping relation to each other. A cam member generally .4 indicated at 68 is pivotally mounted on bracket wall portion 64 and a second cam member 70 is pivotally mounted on bracket wall portion 66. The cam 68 includes a cam element 72 having an end portion 74 of acute angular configuration. The cam 70 similarly includes a cam element 76 having an end portion 78 of acute angular configuration. The cam elements 72 and 76 lie in a common plane, whereby movement of either cam element out of its neutral position will cause the acute angular end portion thereof to move into the path of movement of the other cam member, to thereby prevent movement of the other cam member.

The respective cam elements 7 2, 76, respectively, include arcuate surfaces 72, 76 of uniform radius having the pivotal axis of each respective cam 68, 70 as a center from which the radius of each respective arcuate surface extends. Arcuate surfaces 72, 76 each have the same radius. The distance between the pivotal axes of the two cams 68, 70 is less than the sum of the radii of the two cam elements 72, 76.

Cam 68 also includes a planar portion or projection 80 while the cam 70 includes a planar portion or projection 82. Each of the cams 68, 70 is supported for pivotal movement by a stud or pin member 83 which extends through the corresponding bracket wall portion 64 or 66. Each cam 68, 70 is provided with a passage or bore which receives the stud or pin member 83. Nut members 84, 85 are secured to opposite ends of the stud or pin member 83 to retain the cam member on the stud and also to retain the stud member on the bracket wall portion 64, 66. A spiral spring is coaxially positioned within the bore or passage in each cam member provided for the stud 83, the spiral spring being anchored at one end to the cam surface and at the other end to a stationary surface in such manner as to bias the cam into the normally neutral position against stop member 77, such as that shown in FIG. 3 of the drawing, in which both of the cams 68 and 70 are shown in their neutral positions.

Internally of each of the switch housings 44 and 44 and not shown in the drawings, is a movable contact assembly which is moved upwardly in response to energization of a solenoid within the switch housing to effect closing of the switch. The movable contact structure of switch 10 includes a pair of oppositely disposed outwardly extending projections or arms 86, one of which is in underlying relation to the planar portion 80 of cam member 68. Similarly, the movable contact structure of switch 10 includes a pair of oppositely disposed arms 86', one of which is in underlying relation to the planar portion 82 of cam 70. Thus, for example, when the electrical solenoid of switch 10 is energized to raise the movable contact structure thereof into electrically connecting relation with the stationary contact structure of switch 10, the arm 86 moves upwardly with the movable contact str-ucture and abuts against the planar portion 80 of cam 68, in so doing causing cam 68 to pivot in a counterclockwise direction with respect to the view shown in FIG. 5 about its pivotal support to thereby move the angular tipped portion 74 of cam 68 into the path of movement of cam 70. Springs 88 (FIG. 2) bear against the projections 86, 86 to bias the contact assemblies of the respective switches downwardly to a normally open position. The upper ends of springs 88 are received in spring seats carried by the switch covers 46, 46'. Upon energization of the switch actuating solenoid, the movable contact assembly moves upwardly against the bias of springs 88 into engagement with the banks of stationary contacts carried by the undersurface of the switch cover, to thereby close the circuit through the switch. When the solenoid is deenergized, the movable contact assembly is returned to open position by the force of springs 88.

When cam 68 moves into the path of pivotal movement of cam 70 as just described, cam 70 is prevented from rotating. Hence, if, due to some inadvertence, the

other switch is energized while switch 10 is still energized, the extension portion of projection 86 which moves with the movable contact assembly of switch 10 will be unable to move upwardly since it will abut against the planar portion 82 of the cam 70 and will be prevented from further upward movement due to the fact that the cam 70 is locked against rotation. The limited movement of cam 70 which occurs before it abuts against the tipped end 74 of cam 68 in the situation just described is not sufficient to permit closure of switch 10'.

It will be obvious from the foregoing that if switch 10' is energized before switch 10, the cam 70 associated with switch 10' will be rotated to a position in which it mechanically prevents closing of switch 10 while switch 10' is closed.

If switch 10 or 10' which has been energized becomes deenergized, the corresponding movable contact assembly drops down out of its circuit making position, in so doing causing the projection 86 or 86' to drop down, permitting the associated cam 68 or 70 to return to its neutral position under the influence of its biasing spring.

As previously pointed out, it is important that only one of the switches 10 or 10 be closed at the same time since if both switches were closed at the same time a short circuit'would occur across the two simultaneously closed switches. The interlock arrangement hereinbefore described, insures that only one or the other of the switches 10 or 10' can be closed at any given time. Furthermore, the construction of the interlock and the mounting arrangement therefor maintains the cams 68 and 70 in a constantly fixed relation to each other thereby insuring proper interlocking action despite any variations in the spacing between the switches 10 and 10'.

It is obvious from the foregoing description and drawing that the detailed arrangement and construction of the various elements may be modified considerably without departing from the spirit of the invention which must not be considered as limited strictly to the constructions shown and described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A mechanism for interlocking two devices whereby only one of said devices may be in operative position at a given time, comprising support means adapted to be connected to each of said devices, a first and a second cam means supported for pivotal movement each about a separate pivotal axis by said support means and in contiguous relation to each other, each cam means including a cam element movable about its corresponding pivotal axis and in a common plane with the cam element of the other cam means, said support means including fixed stop means for each cam means, means biasing each cam means to unactuated position against its corresponding stop means, each cam element when in unactuated position and its respective pivotal axis lying on an opposite side than the other cam element and its pivotal axis of a plane midway between said pivotal axes, each cam element including a convex arcuate surface of uniform radius equal to the corresponding radius of the other cam element and having the pivotal axis of the respective cam element as the center from which the respective radius extends, the distance between the pivotal axes of the two cam elements being less than the sum of the radii of the two cam elements whereby a predetermined movement of a given cam element about its pivotal axis away from its unactuated stop position and toward the other cam element causes the convex arcuate surface of the given cam element to move into interfering relation to the other cam element to prevent movement to operative position of the device associated with said other cam element, a cam operating means operatively associated with each of said devices, each of said cam operating means being movable upon movement of its associated device into operative position to eifect movement of its associated cam element into interfering engagement with the other of said cam elements whereby to prevent actuation of the device associated with the other of said cam elements to operative position.

2. A mechanism as defined in claim 1 in which each cam element includes an angular cam portion movable into interfering blocking relation to the other cam element upon actuation of its associated device into operative position prior to actuation of the device associated with the other cam element.

3. A mechanism as defined in claim 1 in which each cam means includes a projection lying on an opposite side of a pivotal axis of the respective cam means from the cam element of the respective cam means, said projection being adapted to be engaged by a corresponding cam operating means whereby to eifect pivotal movement of said cam means about said pivotal axis.

4. A mechanism as defined in claim 1 in which said two devices are electrical switches.

5. A mechanism for interlocking two electrical switches whereby only one of said switches may be in operative position at a given time, comprising a bracket means adapted to be connected to the housing of each of said switches, a first and a second cam means supported for pivotal movement each about a separate pivotal axis by said bracket means and in contiguous relation to each other, each cam means including a cam element movable about its corresponding pivotal axis and in a common plane with the cam element of the other cam means, said support means including fixed stop means for each cam means, means biasing each cam means to unactuated position against its corresponding stop means, each cam element when in unactuated position and its respective pivotal axis lying on an opposite side than the other cam element and its pivotal axis of a plane midway between said pivotal axes, each cam element including a convex arcuate surface of uniform radius equal to the corresponding radius of the other cam element and having the pivotal axis of the respective cam element as the center from which the respective radius extends, the distance between the pivotal axes of the two cam elements being less than the sum of the radii of the two cam elements whereby a predetermined movement of a given cam element about its pivotal axis away from its unactuated stop position and toward the other cam element causes the convex arcuate surface of the given cam element to move into interfering relation to the other cam element to prevent movement to operative position of the switch associated with said other cam element, a cam operating means operatively associated with each of said switches, each of said cam operating means being movable upon movement of its associated switch into operative position to elfect movement of its associated cam element into interfering engagement with the other of said cam elements whereby to prevent actuation of the switch associated with the other of said cam means to operative position.

6. A mechanism for interlocking two electrical switches as defined in claim 5 in which each cam operating means is carried by and movable with the movable contact assembly of the corresponding switch.

7. A mechanism for interlocking two electrical switches as defined in claim 5 in which each cam element includes an angular cam portion movable into interfering blocking relation to the other cam element upon actuation of its associated device into operative position prior to actuation of the device associated with the other cam element.

8. A mechanism for interlocking two electrical switches as defined in claim 5 in which each cam means includes a projection lying on an opposite side of a pivotal axis of the respective cam means from the cam element of the respective cam means, said projection being adapted to be engaged by a corresponding cam operating means whereby to effect pivotal movement of said cam means about said pivotal axis.

9. In combination, a first and a second electrical switch each including stationary contact means, movable contact means and a housing for said stationary and movable contact means, a bracket means connected to the housing of each of said switches, first and second cam means supported for pivotal movement each about a separate pivotal axis by said bracket means and in contiguous relation to each other, each cam means including a cam element movable about its corresponding pivotal axis and in a common plane with the cam element of the other cam means, said bracket means including fixed stop means for each cam means, means biasing each cam means to unactuated position against its corresponding stop means, each cam element when in unactuated position and its respective pivotal axis lying on an opposite side than the other cam element and its pivotal axis of a plane midway between said pivotal axes, each cam element including a convex arcuate surface of uniform radius equal to the corresponding radius of the other cam element and having the pivotal axis of the respective cam element as the center from which the respective radius extends, the distance between the pivotal axes of the two cam elements being less than the sum of the radii of the two cam elements whereby a predetermined movement of a given cam element about its pivotal axis away from its unactuated stop position and toward the other cam element causes the convex arcuate surface of the given cam element to move into interfering relation to the other cam element to prevent movement to operative position of the switch associated with said other cam element, a cam operating means operatively associated with each of said switches, each of said cam operating means being movable upon movement of its associated switch into operative position to effect movement of its associated cam element into interfering engagement with the other of said cam elements, whereby to prevent actuation of the switch associated with the other of said cam elements to operative position.

10. The combination defined in claim 9 in which each carn operating means is carried by and movable with the movable contact means of the corresponding switch.

References Cited UNITED STATES PATENTS 2,359,614 10/1944 Brooks ZOO-50.3 X 3,210,491- 10/1965 Di Marco 200-503 3,233,052 2/1966 Contal 200-503 3,432,628 3/ 1969 Puetz 200-50 ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant Examiner 

